mapj1:

Do we want to save all of the people all of the time, or is it more like car safety where there is a balance  to strike with what is reasonable versus inconvenience like trips firing when they should not ?

Perhaps  is worth noting that the DNOs work on live LV most of the time, including in holes full of water, and their networks break all sorts of BS7671 rules about earths, neutrals, discrimination, disconnection times, but with few incidents, suggesting BS7671 is over cautious.

Faults on large cables are rarer, as they are well, larger, and more obvious and also folk will not normally be holding onto anything fed directly by it, but rather things fed via a final circuit more finely protected.  (not true if you are the sort in the habit of opening the bus bar chamber to obtain a  temporary power of opportunity with some wingnuts but that is your own look-out - bring your own gloves....)


I agree it would be good to know what the assumptions are, for there surely are some, but the accident record suggests they are not that unreasonable.

Mike.

Well, I see videos of fualts breaking rather quickly on UK networks, where on other parts of the world they take their jolly time. UK DNOs know their craft in comparison.


I think we can save people all of the time, with less when all is summed than is being asked of right now...


 

mapj1:

Do we want to save all of the people all of the time, or is it more like car safety where there is a balance  to strike with what is reasonable versus inconvenience like trips firing when they should not ?

Perhaps  is worth noting that the DNOs work on live LV most of the time, including in holes full of water, and their networks break all sorts of BS7671 rules about earths, neutrals, discrimination, disconnection times, but with few incidents, suggesting BS7671 is over cautious.

Faults on large cables are rarer, as they are well, larger, and more obvious and also folk will not normally be holding onto anything fed directly by it, but rather things fed via a final circuit more finely protected.  (not true if you are the sort in the habit of opening the bus bar chamber to obtain a  temporary power of opportunity with some wingnuts but that is your own look-out - bring your own gloves....)


I agree it would be good to know what the assumptions are, for there surely are some, but the accident record suggests they are not that unreasonable.

Mike.

Well, I see videos of fualts breaking rather quickly on UK networks, where on other parts of the world they take their jolly time. UK DNOs know their craft in comparison.


I think we can save people all of the time, with less when all is summed than is being asked of right now...